1. Field of the Invention
The present invention relates to a construction machine using both engine power and electric power.
2. Description of the Related Art
An excavator shown in FIG. 7 is configured such that an upper rotating body 2 is mounted on a crawler type lower traveling body 1 so as to be rotatable about an axis of ordinate and an excavating apparatus 9 equipped with a boom cylinder 6, an arm cylinder 7 and a bucket cylinder 8 for actuating a boom 3, an arm 4 and a bucket 5 respectively is attached to a front portion of the upper rotating body 2.
A cabin 10 is mounted on a front left side of the upper rotating body 2 and a counterweight 11 is mounted on a rear end portion of the upper rotating body 2.
Behind the cabin 10 is mounted a partition wall 12 in a transverse direction. An engine room 13 is formed between the partition wall 12 and the counterweight 11 and an engine 14 as a power source is installed in the engine room 13 (see Japanese Patent No. 3649147).
FIG. 8 is a block diagram of a drive system and a control system in the case where the excavator in question is configured as a hybrid type.
A variable capacity type hydraulic pump 16 and a generator-motor 17 which in a single unit performs both a generator function and a motor function are connected in parallel to the engine 14 via a power divider (PTO as the case may be) 15 and are driven simultaneously by the engine 14.
The boom, arm and bucket cylinders 6 to 8 shown in FIG. 7, as well as hydraulic actuators such as right and left hydraulic motors for traveling (not shown), are connected to the hydraulic pump 16 via control valves (provided for each actuator, but are here shown as an assembly of plural control valves) 18 and are driven with pressure oil fed from the hydraulic pump 16.
An electric power storage device 20 such as a secondary battery is connected to the generator-motor 17 via an inverter/converter 19.
The inverter/converter 19 not only switches the generator function and the motor function of the generator-motor 17 from one to the other but also controls generated power or an electric current or torque in the motor in accordance with a command issued from a controller 21 and controls the charge and discharge of the electric power storage device 20 in accordance with excess or deficiency of the generator output in the generator-motor 17.
In accordance with the charge quantity in the electric power storage device 20 and the number of revolutions of the generator-motor 17 the controller 21 outputs an engine speed command, a pump volume command for the hydraulic pump 16 and a torque command for the generator-motor 17.
In this configuration, where the power required of the hydraulic pump 16 is large, the generator-motor 17 performs the motor function using the electric power stored in the electric power storage device 20 to make up for the engine output, while where the required power is small, the generator-motor 17 performs the generator function to store electric power in the electric power storage device 20. In this way an energy-saving operation inherent in the hybrid type is performed.
As to the layout of unit in the hybrid type excavator, it is disclosed in Japanese Patent Laid-Open No. 2004-169465.
In the case of a hybrid type excavator it is necessary that hybrid devices such as the generator-motor 17, inverter/converter 19, electric power storage device 20 and controller 21, in addition to engine-related and hydraulic devices (hydraulic pump 16, control valve 18, as well as hydraulic devices including a fuel tank, a working oil tank and a control valve, working oil tank, cooling fan, radiator, oil cooler, etc.), be installed in a space of the same size as a conventional hydraulic excavator.
That is, as many unit as possible must be packed into a limited space.
In this regard, in the conventional excavator, as shown in FIG. 7 and Japanese Patent No. 3649147, a partition wall 12 is provided in a rear portion of the upper rotating body 2 to define an engine room 13 in the rear portion of the upper rotating body 2.
On the right side of the engine room 13 is formed an unit room in which hydraulic devices are mainly installed. The unit room and the engine room 13 are also partitioned from each other using a dedicated partition wall.
Thus, in the conventional hybrid excavator, the dedicated partition wall and the surrounding space are wasteful and this wasteful space narrows an effective volume of the unit mounting space which is originally narrow, making the layout of unit more difficult.
In such a hybrid excavator it is preferable that the inverter/converter 19 as hybrid unit be disposed in the engine room 13 for facilitating electric connection with other hybrid unit (e.g., generator-motor 17) disposed outside the cabin 10 and for ensuring a required internal space of the cabin 10.
In this case, however, a temperature is apt to rise with hot air present in the engine room 13, with a consequent likelihood of malfunction.
According to a known countermeasure to this point, as disclosed in Japanese Patent Laid-Open No. 2004-169465, the inverter/converter 19 is disposed in an intake compartment in the engine room 13 and cooling is performed by utilizing air introduced with a cooling fan which is installed in the intake compartment for air-cooling a radiator and an oil cooler.
On the other hand, in Japanese Patent No. 3649147 there is disclosed a technique such that the electric power storage device 20 is installed behind the cabin 10 and cold air for air conditioning present within the cabin 10 is fed to the rear side of the electric power storage device 20 through a duct disposed through the partition wall 12. It may be effective to apply this technique to the inverter/converter 19.
The body of the inverter/converter 19 is usually accommodated within a box-like casing.
According to the former technique which utilizes air introduced by the cooling fan, the cooling air is brought into contact with an outer surface of the casing and thus the body of the inverter/converter is cooled indirectly via the casing. Therefore, a body cooling effect is not sufficient and an increase in temperature of the body to a high level is unavoidable particularly in the summer season.
On the other hand, according to the latter technique which utilizes cold air present within the cabin, it is necessary that a hole for passage therethrough of the duct be formed in each of the cabin 10 and the partition wall 12, so that not only machining is troublesome and the cost rises, but also the space of the engine room is diminished by the duct piping space for example, with a consequent fear of obstructing the layout of other unit.